Abstract
BACKGROUND: There is limited research comparing both performance and brain control of walking between older adults with progressive and relapsing-remitting MS. OBJECTIVE: This study compared older adults with progressive and relapsing-remitting MS for differences in prefrontal cortex (PFC) activation in single- and dual-task-walking and practice-related effects on neural efficiency, walking, and cognitive performances. METHODS: Older adults with progressive (n = 32, age=65±6ys) and relapsing-remitting (n = 63, age=65±4ys) MS completed three conditions (single-task walk, single-task-alpha, i.e., cognitive interference task, and dual-task-walk) with three repeated trials wherein we measured PFC oxygenated hemoglobin (HbO(2)), stride velocity and letter generation rate. Task, trial, and group effects and interactions were analyzed using linear mixed effects models. RESULTS: The task-related (i.e. single-to-dual task walking) increase in PFC HbO(2) was greater in progressive than in relapsing-remitting MS (p < 0.001), while the practice-related decrease in dual-task PFC HbO(2) was smaller in progressive than in relapsing-remitting MS (p < 0.001). Progressive MS was associated with slower stride velocity overall, but repeated trials resulted in faster stride velocity and correct letter generation rate for both groups. CONCLUSIONS: Practice-related improvements in cognitive and motor performances coupled with reduced PFC HbO(2) over dual-task walking trials suggest attenuated improvements of efficiency in brain control of attention-demanding locomotion in progressive MS.